1. Field of the Invention
The invention relates to an apparatus and a process for the quasi-continuous treatment of particulate materials.
2. Description of the Prior Art
Various apparatuses serving for the batchwise and/or quasi-continuous treatment of a particulate material are known, for example fluidized-bed apparatuses, as disclosed, for example, in CH-A 686 343, and mixing and stirring apparatuses, as disclosed, for example in WO-A 91/06365. Depending on the type of material to be treated and on the product to be produced therefrom, these known apparatuses can be used independently of one another or can be combined with one another in a so-called multicell apparatus.
In fluidized-bed apparatuses of the above-mentioned type, the particulate material is fluidized by means of gas, in particular air, and subjected to a treatment thereby. This may consist, for example, exclusively of drying of the material. Frequently, however, the material is first sprayed with a liquid in the fluidizing space and provided with a coating or granulated and then dried. In comparison, the mixing and stirring apparatuses according to WO-91/06365 are intended exclusively for granulation and/or mixing of a material with a fluid, for example water, an aqueous solution or an organic solvent.
Both apparatuses are used in combination with one another for the preparation of products for the formation of medicaments, foods, agrochemicals or seed pellets.
For the preparation of granules intended, for example, as a medicament or as a component of a medicament, for example at least one carrier substance, a binder and at least one pharmaceutical active substance can be mixed with one another in the dry state and the mixture is then moistened for granulation. The intermediate product thus prepared can then be further fed to a fluidized-bed apparatus of the above-mentioned type for further processing, for example drying.
If the purity of the particulate material to be processed in a multicell apparatus has to meet high requirements, it is often necessary, in particular when changing the materials processed, for the operator to clean the various systems of the apparatus, which is effected by opening the corresponding containers and cleaning the components removed. If toxic or otherwise health-hazardous materials were processed, opening of the various containers and removal of parts can cause contamination of the environment, contamination of the material and danger to the person or persons cleaning the container. In this context, it has been found, particularly in the case of pharmaceutical production plants that the opening of the various containers and the removal of parts for cleaning purposes can also cause undesired contamination of the plant with impurities from the environment, so that in this case additional measures have to be taken for cleaning the plant. It is true that EP-0 781 949 and U.S. Pat. No. 3,138,167 disclose fluidized-bed apparatuses or mixers which permit cleaning of the associated container with the aid of special cleaning nozzles without opening of said container. However, such cleaning means are not known for mixing and stirring apparatuses of the first-mentioned type.
Furthermore, in the preparation of a product, it is usual first to prepare, for test purposes, relatively small amounts of an end product, whose masses are, for example, of the order of a few kilograms. When the commercial utilization of the product begins, larger amounts of the product are to be prepared according to requirements. For the commercial production, larger apparatuses in which batches having masses of the order of 100 kg or more can be treated will then be used.
This procedure has the disadvantage that the preparation of a product requires several plants of different sizes, whose procurement and installation necessitate high capital costs. If the treatment of a material is carried out first in small apparatuses and then in larger apparatuses, it is necessary to determine new process parameters, in each case by further experiments, for the change of apparatus also frequently referred to as xe2x80x9cscale-upxe2x80x9d, in order to be able to produce the product economically and reproducibly with the desired quality. These experiments are very time-consuming and also expensive. Moreover, the known apparatuses and plants are generally formed in such a way that manipulations to be performed by at least one person are required at least for introducing the material batch and removing the end product. These known apparatuses and plants therefore cannot be operated fully automatically and are not very suitable for continuous 24-hour operation. A further disadvantage is the narrow application range of the installed plants.
It is the object of the invention to eliminate disadvantages of the above-mentioned apparatuses and to propose a novel multicell apparatus which in turn can be cleaned and rendered absolutely hygienic without opening and dismantling of components of the apparatus, i.e. with little expenditure of labor and time. The apparatus should moreover be formed in such a way that it can be operated fully automatically.
This object is achieved, according to the invention, by a multicell apparatus for the batchwise, in particular quasi-continuous, treatment of a particulate material, comprising the following units:
a first container for receiving the premixed material,
a conveyor system connected to the outlet of the container and containing a metering device and a weigher device,
a mixing and stirring means connected in the process direction to the conveyor system,
a homogenizing device downstream of the mixing and stirring means,
a fluidized-bed apparatus having at least two containers for drying and possibly granulation and/or coating of the material,
a product separator connected to the outlet of the fluidized-bed apparatus and
a second container for receiving the end product,
wherein all units of the apparatus are water-tight, that a cleaning system which permits cleaning of the entire apparatus without opening of the various units of the apparatus is present, for which purpose in each case at least one cleaning nozzle connected to a central cleaning system is arranged
in the feed pipe and discharge pipe of the mixing and stirring means,
in the homogenizing device,
in the containers of the fluidized-bed apparatus,
in the product separator and
in the end product container,
and wherein these cleaning nozzles are formed in such a way that, during cleaning of the apparatus, they can be extended into the interior of the corresponding unit of the apparatus and, during treatment of the material, can be completely retracted into the wall bounding said interior.
The multicell apparatus according to the invention is suitable for batchwise and in particular quasi-continuous operation, i.e. for the continuous processing of batches following one another in rapid succession, for example for the preparation of readily flowable granules which are suitable for filling into capsules, sachets and/or for further processing to give tablet-like products for the pharmaceutical, fine chemical and food industries.
The apparatus according to the invention is a multifunctional system which combines the process steps of batch introduction, metering, mixing/granulation, drying (preliminary and subsequent drying) and product collection and possibly additionally the process steps of moist sieving (after mixing/granulation), coating, admixing of additives, dry sieving (after drying) and product cooling with one another in a very compact design. The individual batches are conveyed inside the apparatus through a product path which is hermetically sealed from the outside and in which an internal pressure lower than ambient pressure may additionally prevail, at least in sections. This, together with the cleaning means defined in more detail below, permits contamination-free operation both with aqueous and with organic formulations.
The apparatus is moreover designed for continuous use and meets the high hygiene requirements of the pharmaceutical industry with respect to the performance of the operations of metering, mixing, granulation and drying. The apparatus according to the invention is preferably completely automatically controlled.
The preparation of granules is effected as a rule using water but, with the use of a solvent recovery system providing adequate environmental protection, can also be carried out by means of organic solvents.
In quasi-continuous operation, the initially introduced total batch is divided in a batch container metering system into the individual subunits. The subunits may be 2-15 kg, depending on the size of the apparatus. A substantial advantage of the apparatus according to the invention is therefore the fact that the individual batches always remain constant in the case of apparatuses of the same size and that an increase in the production rate is also possible without problems using the same apparatus, in particular by increasing the number of batch throughputs per unit time. For the user, this means an important economic advantage since in this case it is possible to dispense with the expensive change of apparatus and the time-consuming scale-up experiments in standard operations of mixing, granulation and drying.
Below, the invention is described in more detail with reference to embodiments shown in the drawings.